The Constant Gardener by John le Carré.

Justin Quayle is a British diplomat, a member of Her Majesty’s foreign service, stationed in Nairobi, Kenya. Middle-aged and upper-middle-class, Quayle personifies Britain’s traditional political and social establishment, and while conscientious enough in his professional duties, he devotes his free time to his garden, cultivating temperate flowers which grow well in Kenya’s highlands. His much younger wife, Tess, is the opposite, a crusading lawyer who is very much the antiestablishment figure. Empathizing with the majority of Africans—poor and black—she is deeply committed to social justice. With Arnold Bluhm, a Belgium African doctor, she discovers that a major Swiss pharmaceutical firm, amorally pursuing profits, had, in connivance with other business interests and the Kenyan government, embarked on a campaign to distribute Dypraxa, a new antitubercular drug, to Africa’s poor. The drug, while promising in the long run, has been released without sufficient testing and even with willfully inaccurate tests, and Africa’s poor are to be the guinea pigs. Too many political and economic interests are threatened by Tess and Arnold’s exposures, and they are brutally murdered. Justin is apparently intentionally unaware of the extent of Tess’s involvement, spending his time tilling his garden.